1. Field of the Invention
The invention relates to a workpiece positioning arrangement, which comprises a positioning device for positioning a workpiece as well as a decoupling device for the decoupled storage of the positioning device, wherein the decoupling device comprises a carrier element, on which the positioning device is arranged, and a base element, on which the carrier element is supported.
2. Background
In many fields of technology, workpieces to be machined are machined or already machined workpieces are inspected with the help of machining devices or inspection machines (or more generally: a processing system), in which a tool head or inspection head is moved relative to the workpiece to be machined or inspected. For purposes of machining or inspecting (or more generally: processing), the tool head/inspection head is here either moved by corresponding actuators, or the workpiece is moved by actuators in a movably arranged workpiece receptacle. It is basically also conceivable that both the tool head/inspection head and the workpiece be moved. Movability here relates to a machine base body or to a workshop, factory or the like, in which the machine is set up.
In cases where especially small structures must be processed (fabricated and/or inspected), use is usually made of the basic principle in which the respective workpiece is moved relative to a stationary base. This is also based in particular on considerations having to do with the respectively present masses: As a rule, the respective workpiece comprises a comparatively small mass (even when also including the mass of the tool receptacle device and the like); in contrast, the respective tool head/inspection head comprises a large mass, in particular relative to the workpiece. It must here be considered that especially small structures typically require the use of expensive tool heads/inspection heads that deliver enough precision; as a rule, this is accompanied by a comparatively large overall size and/or mass. One example for the latter involves processing semiconductor structures (semiconductor microstructures), e.g., microprocessors, but also processing mechanical microstructures.
Another problem in the area of microstructures is here that already comparatively small vibrations can lie on the order of magnitude of the structures to be processed in terms of their amplitude, unless suitable countermeasures are introduced. Such vibrations are naturally to be avoided, since they can render the workpiece unusable or unusable measuring results could result. Vibrations like these can be introduced into the system from outside, e.g., jolts caused by passing operating personnel or vibrations caused by nearby machines. In order to sufficiently reduce vibrations here, decoupling devices are typically used, for example damping elements, on which the actual processing system is supported. The latter bring about a mechanical decoupling between the surrounding space and processing machine, at least within certain limits.
Another problem has to do with disturbances, in particular vibrations, which are caused by the processing system itself. This is because the masses to be moved here also result in acceleration processes or repositioning processes for the masses, which inevitably lead to mechanical vibrations. In addition, the dynamic reaction forces can be conveyed from the positioning device via the carrier element to the base element and its substrate (frame on which the base element is supported), wherein the base element and substrate then conversely exert counterforces onto the carrier element and positioning device based on the action and reaction principle. As a whole, this disadvantageously impairs the stability and precision of the positioning. This effect can sometimes even be enhanced further if active stabilizing devices are provided between the base element and carrier element. The problems described above are encountered on an elevated scale with increasing accelerations or traveling speeds. At the present time, the latter most often constitute the limiting factor on increasing the processing rate of the workpieces. This poses a problem, since lower processing rates lead to elevated costs in manufacturing the respective microstructures. Especially problematical is a case where smaller structures are to be processed as the result of technological progress, for example, new chip generations with reduced structural dimensions.
Various decoupling devices have already been proposed in prior art for diminishing vibrations. One example of the latter is Japanese Patent Specification H2-201913A, which proposes a lighting device that is decoupled from the environment in terms of vibration. An optical system can be moved by means of a moving means relative to a table, on which the workpiece to be machined is secured. Air retaining means are provided between the table and a pedestal carrying the table (along with optical system). The air retaining means are located in a horizontal plane, which separates the pedestal from the table. This results in a decoupling in the vertical direction. Further provided is a frame around the table, wherein the frame is fixedly joined with the pedestal. Air retaining means are also provided between the lateral frame walls and lateral table walls. This enables an improved mechanical decoupling from movements that run parallel to the horizontal plane. A particularly good damping and vibrational decoupling in three dimensions is realized overall. However, the problem of disturbances generated by high traveling rates or high accelerations during the relative movement of the table and optical system is at best inadequately addressed, if at all.